Jeff
I had a similar problem with my 1991 Audi 90,
but after idling rough the engine also stalled and
would only restart after 10-15 mins. If the weather was hot above ~27C
it would stall again after approx 15mins untill outside temp dropped
below ~25C.
Did you notice if the FP is producing different (pulsating) noise? Mine
was.
I changed both FP and FP relay but I still had the problem.
It turned out to be power supply to the fuel pump.
Then I installed anther relay under the rear seat and new wires.
Now the new relay gets activated by the original FP relay and
it (the new relay) supplies power to the FP.
Since then I had no probs.
Mark